Along with exhaustion of fossil fuels, the use of renewable energy sources such as solar energy and wind energy attracts more and more attention, however, due to intermittency these renewable energy sources cannot continuously main the supply to the power grid, so that the development of energy storage systems is vital to employ renewable energy sources. Due to abundant reserves and wide distribution of sodium resources, sodium ion batteries have a potential advantage of low cost, more importantly, taking sodium ions as carriers to find new electrochemical reaction mechanisms and new materials to realize the goal of further cost-reduction. For example, sodium and aluminum will not be subject to alloying reaction so that the aluminum foil can serve as anode current collectors (since lithium can alloy with aluminum the anode current collector of lithium ion battery cannot use the aluminum foil), thus the problem that the oxidation of the current collector caused by overdischarge of the sodium ion battery is effectively avoided, and the battery is convenient to store and transport.
The development and application of high-performance and low-cost anode materials is an important step for the commercialization of sodium ion batteries. At present, commercialized lithium ion batteries mainly use the graphite materials as mainstream anodes, but because of the thermodynamics reason, sodium ions are difficult to embed between the graphite material layers, and cannot serve as the anode of the sodium ion batteries.
In numerous researched anode materials of the sodium ion batteries, hard carbon becomes the anode material with the largest application prospect due to its high specific capacity, low sodium storage potential and the like. The precursors for preparing the hard carbon material mainly comprise cellulose, saccharides, furan resin, phenolic resin, polyvinylidene chloride and the like, thus the hard carbon is high in price as these precursors have high price and low carbon yield, together with the complex hard carbon preparing processes, limiting the large-scale application of the hard carbon material.
According to embodiments of the invention, an amorphous carbon material with adjustable disorder degree, simple preparation method, low cost, high carbon yield and easy available raw materials has been prepared by taking low-cost coal as a main raw material, and the obtained carbon material is particularly suitable for serving as the anode material of the sodium ion secondary batteries.